[PATCH] progress: don't print if !isatty(2).

[Avery Pennarun <apenwarr@gmail.com>]

If stderr isn't a tty, we shouldn't be printing incremental progress
messages.  In particular, this affected 'git checkout -f . >&logfile' unless
you provided -q.  And git-new-workdir has no way to provide -q.

Signed-off-by: Avery Pennarun <apenwarr@gmail.com>
---
 progress.c |    6 ++++--
 1 files changed, 4 insertions(+), 2 deletions(-)

diff --git a/progress.c b/progress.c
index 3971f49..4d9f416 100644
--- a/progress.c
+++ b/progress.c
@@ -211,9 +211,11 @@ int display_progress(struct progress *progress, unsigned n)
 struct progress *start_progress_delay(const char *title, unsigned total,
 				       unsigned percent_treshold, unsigned delay)
 {
-	struct progress *progress = malloc(sizeof(*progress));
+	struct progress *progress = NULL;
+	if (isatty(2))
+		progress = malloc(sizeof(*progress));
 	if (!progress) {
-		/* unlikely, but here's a good fallback */
+		/* use a simple fallback */
 		fprintf(stderr, "%s...\n", title);
 		fflush(stderr);
 		return NULL;
-- 
1.7.9.dirty